DEBT - Trust Preferred Securities (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Trust Preferred Securities
Trust preferred securities	$ 1,700	$ 1,700
Liquidation value	2,584
Junior subordinated debentures owned by the Trust, amount	$ 2,590
Citigroup Capital III
Trust Preferred Securities
Securities issued (in shares)	194,053
Liquidation value	$ 194
Coupon rate (as a percent)	7.625%
Common shares issued to parent (in shares)	6,003
Junior subordinated debentures owned by the Trust, amount	$ 200
Citigroup Capital XIII
Trust Preferred Securities
Securities issued (in shares)	89,840,000
Liquidation value	$ 2,246
Coupon rate (as a percent)	7.875%
Common shares issued to parent (in shares)	1,000
Junior subordinated debentures owned by the Trust, amount	$ 2,246
Citigroup Capital XVIII
Trust Preferred Securities
Securities issued (in shares)	99,901
Liquidation value	$ 144
Coupon rate (as a percent)	6.829%
Common shares issued to parent (in shares)	50
Junior subordinated debentures owned by the Trust, amount	$ 144